In a conventional method of producing SOI wafers, two wafers of monocrystalline silicon having at least one oxidized surface are thermally bonded to one another with the silicon dioxide surfaces and then the one wafer is thinned back.
In the SIMOX ("separation by implanted oxygen") method, oxygen ions are implanted in a monocrystalline silicon wafer, forming, after activation with silicon, a silicon dioxide layer which separates the wafer from a thin layer of silicon.
In another conventional method, silicon is deposited epitaxially on a porous monocrystalline silicon layer and then the porous silicon is oxidized.
In another conventional method, silicon is applied epitaxially to a porous, monocrystalline silicon layer, partially oxidized on its surface, after etching back.
All these conventional methods have in common the high manufacturing costs, caused by high consumption of materials or very expensive process steps, e.g., in the production of thick epitaxial layers.